1. Field of the Invention
The present invention relates to a calibration method for precisely aligning the center of a die entrance bushing with the center of an injection nozzle of an injection molding machine.
2. Description of the Related Art
A conventional injection molding machine in accordance with the prior art shown in FIGS. 7 and 8 comprises a fixed frame 83 defining a tapered opening 84 therein, a die 80 secured to the fixed frame 83 and defining a cavity 82 therein, a die entrance bushing 81 mounted in the die 80 and connecting to the cavity 82 and the tapered opening 84, and an injection nozzle 86 secured to a feed tube 85 which is movable relative to the fixed frame 83 so that the injection nozzle 86 can be moved into the tapered opening 84 of the fixed frame 83 to contact the die entrance bushing 81 so as to inject plastic raw material contained in the feed tube 85 into the cavity 82 of the die 80. The plastic raw material may reversely flow from the die entrance bushing 81 when the center of the die entrance bushing 81 does not register the center of the injection nozzle 86. Therefore, it is important to align the center of the die entrance bushing 81 with the center of the injection nozzle 86.
A conventional calibration method in accordance with the prior art comprises providing a needle 88 on the injection nozzle 86. The feed tube 85 is then moved relative to the fixed frame 83 until the needle 88 contact the die entrance bushing 81 so as to inspect the deviation between the die entrance bushing 81 and the injection nozzle 86 by eyesight. The position of the die 80 is repeatedly adjusted so as to adjust the position of the die entrance bushing 81 for manually aligning the center of the die entrance bushing 81 with the center of the injection nozzle 86. Therefore, the operation of the conventional calibration method is not easily performed, it requires a long period of time for calibrating the center of the die of the injection molding machine. Further, an operator needs to get close to the feed tube 85 so as to calibrate the center of the die of the injection molding machine by eyesight so that the operator is easily injured by the feed tube 85 which is often very hot.
The present invention has arisen to mitigate and/or obviate the disadvantage of the conventional calibration method.
In accordance with one aspect of the present invention, there is provided a calibration method for aligning a center of a die entrance bushing with a center of an injection nozzle of an injection molding machine.
The calibration method includes the following steps: (a) moving a camera to project an image of an injection nozzle of an injection molding machine onto a screen of the camera so as to align a center of the injection nozzle with a center of the screen; (b) moving a die entrance bushing of a die of the injection molding machine relative to the camera to project an image of the die entrance bushing of the die onto the screen of the camera; and (c) moving the die relative to the camera so as to align a center of the die entrance bushing with the center of the screen so that the center of the die entrance bushing aligns with the center of the injection nozzle. The screen includes a cross coordinate mounted thereon, and a plurality of scales mounted thereon.
The calibration method further includes the step of providing at least one mark on a tapered opening of the injection molding machine so as to correct the center of the screen of the camera, wherein the tapered opening is located between the die entrance bushing and the camera.
The calibration method further includes the step of inspecting the distance between the center of the die entrance bushing and the center of the screen so that the distance is used as a distance for moving the die relative to the camera.
The calibration method further includes the step of providing a swing arm pivotally mounted on a fixed frame of the injection molding machine; and mounting the camera on the swing arm.
Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.